Carbon-interfaced nanostructure phase-change memory with capping layer: A strategy for low-thickness variation and reliability

Abstract

In order to overcome the challenges existed in traditional phase change materials and devices in terms of thickness variation, heat dissipation, operating speed and resistance fluctuation, this work introduces a novel phase change device with a thickness of 20 nm C/Sb₂Te (C/ST) heterostructure active region and adding a Ge₂Sb₂Te₅ (GST) capping layer (CL) to achieve high performance. The thickness change rate of the proposed [C/ST]₂+CL is only 0.2 %, the device operating speed is as fast as 5 ns, and the cycle endurance is up to about 8×10⁵ with high resistance ratio and good stability. The power consumption and resistance drift largely decrease to 10 pJ and 0.04, respectively. The Ab initio molecular dynamics (AIMD) simulations show that the C atoms in the amorphous C layer mainly exist in a network form of C rings and C chains. The C layer serves as a confinement medium that limits atomic diffusion, stabilizes the amorphous phase, and mitigates resistance drift, thereby enhancing thermal stability and reducing power consumption. Additionally, the GST CL effectively suppresses elemental segregation, further improving the endurance and reliability of PCRAM devices. This work provides a promising approach for material design and performance optimization for phase-change random access memories.